Thin film transistor array substrate, organic light-emitting display apparatus, and method of manufacturing the thin film transistor array substrate

ABSTRACT

Provided is a thin film transistor including an active layer including a first silicon active layer, a second silicon active layer, and an oxide active layer in a space between the first silicon active layer and the second silicon active layer, a gate electrode on the active layer with a gate insulating layer disposed therebetween, and a source electrode and a drain electrode with an interlayer insulating layer disposed between the gate electrode and the source and drain electrodes, the source and drain electrodes being in contact with the first silicon active layer and the second silicon active layer, respectively.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This is a continuation application of U.S. patent application Ser. No.16/553,240, filed Aug. 28, 2019 (currently pending), the disclosure ofwhich is incorporated herein by reference in its entirety. U.S. patentapplication Ser. No. 16/553,240 is a continuation application of U.S.patent application Ser. No. 16/042,268, filed Jul. 23, 2018, now U.S.Pat. No. 10,403,764, issued Sep. 3, 2019, the disclosure of which isherein by reference in its entirety. U.S. patent application Ser. No.16/042,268 is a continuation application of U.S. patent application Ser.No. 15/622,680, filed Jun. 14, 2017, now U.S. Pat. No. 10,032,933,issued Jul. 24, 2018, the disclosure of which is herein by reference inits entirety. U.S. patent application Ser. No. 15/622,680 is adivisional application of U.S. patent application Ser. No. 14/516,889,filed Oct. 17, 2014, now U.S. Pat. No. 9,698,279, issued Jul. 4, 2017,the disclosure of which is herein by reference in its entirety. U.S.patent application Ser. No. 14/516,889 claims priority benefit of KoreanPatent Application No. 10-2013-0124145 under 35 U.S.C. § 119, filed onOct. 17, 2013, the disclosure of which is incorporated herein byreference in its entirety for all purposes.

BACKGROUND 1. Field

One or more embodiments relate to a thin film transistor arraysubstrate, an organic light-emitting display apparatus, and a method ofmanufacturing the thin film transistor array substrate.

2. Description of the Related Art

Thin film transistor array substrates, which include thin filmtransistors, capacitors, and wirings connecting the thin filmtransistors and the capacitors, are being widely used in flat paneldisplay apparatuses, such as liquid crystal display apparatuses andorganic light-emitting display apparatuses.

In an organic light-emitting display apparatus using a thin filmtransistor array substrate, each pixel is defined by arrangingpluralities of gate lines and data wirings in the form of a matrix. Eachpixel includes thin film transistors, a capacitor, and an organiclight-emitting device connected thereto. The organic light-emittingdevice may emit light by receiving appropriate driving signals from thethin film transistors and the capacitor, and thus may generate a desiredimage.

SUMMARY

Embodiments may be realized by providing a thin film transistor,including an active layer on a substrate, the active layer including afirst silicon active layer, a second silicon active layer, and an oxideactive layer in a space between the first silicon active layer and thesecond silicon active layer; a gate electrode on the active layer with agate insulating layer disposed therebetween; and a source electrode anda drain electrode with an interlayer insulating layer disposed betweenthe gate electrode and the source and drain electrodes, the source anddrain electrodes being in contact with the first silicon active layerand the second silicon active layer, respectively.

Regions of the first silicon active layer and the second silicon activelayer that do not overlap the gate electrode may be doped with N⁺ or P⁺ion impurities.

The source electrode and the drain electrode may not overlap the gateelectrode.

The first silicon active layer and the second silicon active layer mayinclude amorphous silicon or polysilicon.

The oxide active layer may include one or more oxides selected from thegroup of gallium indium zinc oxide (G-I-Z-O), an oxide of zinc (Zn),indium (In), gallium (Ga), tin (Sn), cadmium (Cd), germanium (Ge), orhafnium (Hf), and a combination thereof.

Embodiments may be realized by providing an organic light-emittingdisplay apparatus, including a first transistor which includes a firstgate electrode, a first active layer including a silicon active layerand an oxide active layer, and a first source electrode and a firstdrain electrode, the silicon active layer of the first transistorincluding a first silicon active layer and a second silicon activelayer, and the oxide active layer being between the first silicon activelayer and the second silicon active layer; a second transistor whichincludes a second gate electrode that is formed of a same material andon a same layer as the first gate electrode, a second active layer thatis formed of a same material and on a same layer as the silicon activelayer, and a second source electrode and a second drain electrode thatare formed of a same material and on a same layer as the first sourceelectrode and the first drain electrode; and a light-emitting deviceincluding a pixel electrode, an intermediate layer, and a counterelectrode.

The first transistor may be a switching transistor of the organiclight-emitting display apparatus.

The second transistor may be a driving transistor of the organiclight-emitting display apparatus.

The pixel electrode may be connected to the second source electrode orthe second drain electrode of the second transistor.

Regions of the first silicon active layer and the second silicon activelayer that do not overlap the first gate electrode may be doped with N⁺or P⁺ ion impurities.

The first source electrode and the first drain electrode may not overlapthe first gate electrode.

The first silicon active layer and the second silicon active layer mayinclude amorphous silicon or polysilicon.

The oxide active layer may include one or more oxides selected from thegroup of gallium indium zinc oxide (G-I-Z-O), an oxide of zinc (Zn),indium (In), gallium (Ga), tin (Sn), cadmium (Cd), germanium (Ge), orhafnium (Hf), and a combination thereof.

Embodiments may be realized by providing a method of manufacturing athin film transistor including forming a silicon layer on a substrateand then patterning the silicon layer to form a first silicon activelayer and a second silicon active layer with a space therebetween;forming an oxide semiconductor layer and then patterning the oxidesemiconductor layer to form an oxide active layer in the space betweenthe first silicon active layer and the second silicon active layer;forming a gate insulating layer and forming a gate electrode on the gateinsulating layer; doping the first silicon active layer and the secondsilicon active layer with ion impurities using the gate electrode as amask; and forming an interlayer insulating layer, and forming a sourceelectrode and a drain electrode respectively in contact with the firstsilicon active layer and the second silicon active layer through contactholes in the gate insulating layer and the interlayer insulating layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent to those of skill in the art by describingin detail exemplary embodiments with reference to the attached drawingsin which:

FIG. 1 illustrates a plan view schematically illustrating an organiclight-emitting display apparatus 1 according to an embodiment;

FIG. 2 illustrates an example of an equivalent circuit constituting asingle pixel according to an embodiment;

FIG. 3 illustrates an example of a thin film transistor according to anembodiment;

FIGS. 4A and 4B illustrate comparative examples;

FIG. 5 illustrates a cross-sectional view schematically illustrating theorganic light-emitting display apparatus 1 according to the embodiment;and

FIGS. 6A through 6H illustrate a method of manufacturing an organiclight-emitting display apparatus according to an embodiment.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey exemplary implementations to those skilled in the art.

Like reference numerals refer to like elements throughout.

It will be understood that although the terms “first”, “second”, etc.may be used herein to describe various components, these componentsshould not be limited by these terms. These components are only used todistinguish one component from another.

As used herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

It will be further understood that the terms “comprises” and/or“comprising” used herein specify the presence of stated features orcomponents, but do not preclude the presence or addition of one or moreother features or components.

It will be understood that when a layer, region, or component isreferred to as being “formed on,” another layer, region, or component,it can be directly or indirectly formed on the other layer, region, orcomponent. That is, for example, intervening layers, regions, orcomponents may be present.

Sizes of elements in the drawings may be exaggerated for convenience ofexplanation. In other words, since sizes and thicknesses of componentsin the drawings are arbitrarily illustrated for convenience ofexplanation, the following embodiments are not limited thereto.

When a certain embodiment may be implemented differently, a specificprocess order may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. Expressionssuch as “at least one of,” when preceding a list of elements, modify theentire list of elements and do not modify the individual elements of thelist.

FIG. 1 illustrates a plan view schematically illustrating an organiclight-emitting display apparatus 1 according to an embodiment.

Referring to FIG. 1, a display area DA displaying an image includes aplurality of pixels P and may be formed on a substrate 10 of the organiclight-emitting display apparatus 1 according to the embodiment. Thedisplay area DA may be formed inside an area delimited by a sealing lineSL, and a sealing member (not shown) seals the display area DA along thesealing line SL. Thin film transistors and organic light-emittingdevices constitute the plurality of pixels P and are arranged in thedisplay area DA.

FIG. 2 illustrates an example of an equivalent circuit constituting asingle pixel according to an embodiment.

The plurality of pixels P may include a switching transistor M1, adriving transistor M2, a storage capacitor Cst, and a light-emittingdevice OLED.

According to an embodiment, when a signal of a scan line Sn isactivated, a voltage level of a data line Dm is stored in the storagecapacitor Cst through the switching transistor M1. The drivingtransistor M2 generates a light-emitting current I_(OLED) according to agate-source voltage Vgs, which is determined by the voltage level storedin the storage capacitor Cst, to power the light-emitting device OLED.According to an embodiment, the light-emitting device OLED may be anorganic light-emitting diode.

In order to drive the light-emitting device OLED, the switchingtransistor M1 is sequentially turned on/off by a gate signal which isapplied to the scan line Sn in a predetermined frame of time, and a datavoltage, which is applied to the data line Dm during the switchingtransistor M1 is turned on, is stored in the storage capacitor Cst thatis connected to the driving transistor M2. The switching transistor M1and the driving transistor M2 may be thin film transistors.

Generally, a voltage drop may occur in the scan line Sn as theresolution and size of the organic light-emitting display apparatus 1are increased, and switching transistors M1 included in the plurality ofpixels P may not be turned on/off together in a predetermined period oftime. In order to address such situations and decrease the resistance ofwirings such as the scan line Sn, highly conductive wirings may be usedor a thickness of the wirings may be increased. Also, in order todecrease a parasitic capacitance generated between overlapping wirings,a thickness of an insulator may be increased or a parasitic capacitanceof a thin film transistor that is connected to the wirings may bedecreased.

FIG. 3 illustrates an example of a thin film transistor according to anembodiment.

A first transistor 21 according to an embodiment may be formed on asubstrate 110 and a buffer layer 111, and includes active layers 212 a,212 b, and 212 c, a gate insulating layer 113, a gate electrode 214, aninterlayer insulating layer 115, a source electrode 216 a, and a drainelectrode 216 b.

The substrate 110 may be a plastic substrate, such as, for example,polyethylene terephthalate (PET), polyethylene naphthalate (PEN), orpolyimide, or a glass substrate.

The buffer layer 111, for example, for planarizing and blockingpenetration of impurity elements in the substrate 110, may be provided.The buffer layer 111 may be formed as, e.g., a single layer ormultilayers of silicon nitride and/or silicon oxide.

The active layers 212 a, 212 b, and 212 c are disposed on the bufferlayer 111. The active layer 212 includes a first silicon active layer212 a, a second silicon active layer 212 b, and an oxide active layer212 c. The oxide active layer 212 c may be disposed in a space betweenthe first silicon active layer 212 a and the second silicon active layer212 b.

The first silicon active layer 212 a and the second silicon active layer212 b may include amorphous silicon or polysilicon. The first siliconactive layer 212 a and the second silicon active layer 212 b may includedoped regions L1 and undoped regions L2 in which silicon of the firstsilicon active layer 212 a and the second silicon active layer 212 b arerespectively doped and undoped with N⁺ or P⁺ ion impurities. The dopedregion L1 is a region that does not overlap the gate electrode 214, andthe conductivity thereof may be increased by being doped with the ionimpurities, and the electron mobility thereof may be excellent.

The oxide active layer 212 c filling the space between the first siliconactive layer 212 a and the second silicon active layer 212 b may includean oxide semiconductor. For example, the oxide active layer 212 c mayinclude an (In₂O₃)_(a)(Ga₂O₃)_(b)(ZnO)_(c) (G-I-Z-O) layer (where a, b,and c are real numbers respectively satisfying conditions of a≥0, b≥0,and c≥0), and in addition, may include an oxide of a material selectedfrom the group of Groups 12, 13, and 14 metallic elements, such as zinc(Zn), indium (In), gallium (Ga), tin (Sn), cadmium (Cd), germanium (Ge),or hafnium (Hf), and a combination thereof.

A channel region L_(T) of the first transistor 21 is a region in whichthe oxide active layer 212 c and the gate electrode 214 overlap. Thechannel region L_(T) of the first transistor 21 includes undoped regionsL2 of the first silicon active layer 212 a and the second silicon activelayer 212 b.

The gate insulating layer 113 is disposed on the active layers 212 a,212 b, and 212 c. The gate insulating layer 113 may be formed as asingle layer or multilayers of an inorganic insulating layer, and theinorganic insulating layer constituting the gate insulating layer 113may include SiO₂, SiN_(x), SiON, Al₂O₃, TiO₂, Ta₂O₅, HfO₂, ZrO₂, bariumstrontium titanate (BST), or lead zirconium titanate (PZT).

The gate electrode 214 is disposed on the gate insulating layer 113. Thegate electrode 214, for example, may be formed as a single layer ormultilayers of one or more metals selected from the group of aluminum(Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold(Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium(Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), andcopper (Cu).

The interlayer insulating layer 115 is disposed on the gate electrode214. The interlayer insulating layer 115 may be formed as a single layeror multilayers of an inorganic insulating layer, and the inorganicinsulating layer constituting the interlayer insulating layer 115 mayinclude SiO₂, SiN_(x), SiON, Al₂O₃, TiO₂, Ta₂O₅, HfO₂, ZrO₂, BST, orPZT.

The source electrode 216 a and the drain electrode 216 b are disposed onthe interlayer insulating layer 115. The source electrode 216 a and thedrain electrode 216 b are respectively connected to the first siliconactive layer 212 a and the second silicon active layer 212 b throughcontact holes formed in the gate insulating layer 113 and the interlayerinsulating layer 115.

The source electrode 216 a and the drain electrode 216 b may be formedof two or more layers of different metals having different electronmobilities. For example, the source electrode 217 a and the drainelectrode 217 b may be formed of two or more layers of metals selectedfrom the group of Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Ir, Cr, Li, Ca, Mo,Ti, W, Cu, and an alloy thereof.

The doped regions L1 not overlapping the gate electrode may only bedoped with N⁺ or P⁺ ion impurities. The doped regions L1 may have highelectron mobility and the undoped regions L2 may act as an insulator,and the gate electrode 214, the first silicon active layer 212 a, andthe second silicon active layer 212 b may not form a parasiticcapacitance.

Also, in the first transistor 21, the doped regions L1 of the firstsilicon active layer 212 a and the second silicon active layer 212 b maybe doped with ion impurities to decrease the resistance between theoxide active layer 212 c operating as the channel region L_(T) and thesource electrode 216 a and the drain electrode 216 b, and the currentmay be increased when the first transistor 21 is turned on. Since asilicon semiconductor is doped with ions and used, the devicereliability as well as the conductivity may be improved in comparison tothe case of doping an oxide semiconductor with ion impurities.

Furthermore, the oxide active layer 212 c may be included in the channelregion L_(T) of the first transistor 21, and an off-state leakagecurrent of the thin film transistor may be prevented in comparison tothe case of including only silicon in the channel region L_(T).

FIGS. 4A and 4B illustrate comparative examples. In the comparativeexamples of FIGS. 4A and 4B, the same reference numerals as in FIG. 3may denote the same elements.

FIG. 4A illustrates a thin film transistor 22 according to a firstcomparative example of the first transistor 21 of FIG. 3.

The second transistor 22 of FIG. 4A, different from the first transistor21 of FIG. 3, includes a single silicon active layer 222 as an activelayer. The silicon active layer 222 may be formed of a semiconductorincluding amorphous silicon or polysilicon. The silicon active layer 222may include a channel region L_(T) at the center and doped regions L1doped with ion impurities on the outside of the channel region L_(T).The doped regions L1 include a source region (L1 on the left) and adrain region (L1 on the right), the doped regions L1 may be doped withN⁺ or P⁺ ion impurities using a gate electrode 224 as a mask, and theconductivity thereof may be increased.

The doped regions L1 of the silicon active layer 222 are respectivelyconnected to a source electrode 226 a and a drain electrode 226 bthrough contact holes formed in the gate insulating layer 113 and theinterlayer insulating layer 115.

The silicon active layer 222 of the second transistor 22 may haveexcellent electron mobility. However, a leakage current may occur at ahigh voltage, and a voltage stored in the storage capacitor Cst may bechanged or decreased during the driving of the thin film transistor. Thesize of the storage capacitor Cst may be increased in order to preventthe changes in the voltage. However, this may result in the reduction ofan aperture ratio in a limited space of an organic light-emittingdisplay apparatus, and the lifetime of the organic light-emittingdisplay apparatus may be decreased and the power consumption may bedecreased due to an increase in the driving voltage. In order to reduceor prevent the occurrence of the leakage current, an oxidesemiconductor, which has relatively low electron mobility but may haveexcellent leakage current suppression characteristics, may be used as anactive layer of a switching transistor.

FIG. 4B illustrates a third transistor 23 according to a secondcomparative example of the first transistor 21 of FIG. 3.

In the thin film transistor of FIG. 4B, a gate electrode 232 may beformed on the buffer layer 111. Also, an oxide active layer 234 isdisposed on the gate electrode 232 having the gate insulating layer 113disposed therebetween.

The oxide active layer 234 may include an oxide semiconductor. Forexample, the oxide active layer 234 may include an(In₂O₃)_(a)(Ga₂O₃)_(b)(ZnO)_(c) (G-I-Z-O) layer (where a, b, and c arereal numbers respectively satisfying conditions of a≥0, b≥0, and c≥0),and in addition, may include an oxide of a material selected from thegroup of Groups 12, 13, and 14 metallic elements, such as Zn, In, Ga,Sn, Cd, Ge, or Hf, and a combination thereof.

The interlayer insulating layer 115 is disposed on the oxide activelayer 234, and a source electrode 236 a and a drain electrode 236 b arein contact with the oxide active layer 234 through contact holes formedin the interlayer insulating layer 115. In the second comparativeexample of FIG. 4B, the interlayer insulating layer 115 may act as anetch stop layer for protecting the oxide active layer 234 during thepatterning of the source electrode 236 a and the drain electrode 236 b.

The third transistor 23 may include overlap regions Lov, in which thegate electrode 232 overlaps the source electrode 236 a and the drainelectrode 236 b having the insulating layer disposed therebetween, dueto the structure of the thin film transistor. The gate electrode 232,the source electrode 236 a, and the drain electrode 236 b of the overlapregions Lov may respectively act as a capacitor to generate a parasiticcapacitance, and it may be a cause of a RC load during the driving of anorganic light-emitting display apparatus. As illustrated in FIG. 4B,when the third transistor 23 is in an “on” state in a bottom gate-typethin film transistor structure, the oxide active layer 234 acts as aconductor to form the gate electrode 232—the gate insulating layer113—the oxide active layer 234 as a capacitor, and when the thirdtransistor 23 is in an “off” state, the gate electrode 232—the gateinsulating layer 113—the oxide active layer 234—the interlayerinsulating layer 115—the source and drain electrodes 236 a and 236 bform a capacitor to generate a parasitic capacitance.

A thin film transistor may be the third transistor 23, and a value of aresistance connected to the wiring may increase during the driving dueto the parasitic capacitance when the thin film transistor is turned onand off. With respect to a large-sized and high-resolution display,on/off of a switching transistor in a short period of time may beimpaired due to a signal delay caused by the resistance and parasiticcapacitance. Also, when a signal voltage of a data line is stored in astorage capacitor connected to the driving transistor, time for charginga data voltage may be significantly limited due to the signal delaycaused by the resistance and parasitic capacitance of the data line.

When a thickness of the gate insulating layer 113 is increased in orderto decrease the parasitic capacitance, an on-state current of the thinfilm transistor may decrease and, the storage capacitor, which is usedin the circuit of a pixel connected to the switching transistor, may notbe sufficiently charged in a short period of time. Also, a thickness ofsignal wirings, such as the gate electrode 232, may be increased inorder to decrease the signal delay. However, the thickness of the gateinsulating layer 113 may be increased in order to prevent a shortcircuit due to a step height, and a current driving capability of thethird transistor 23 may decrease and a charging time of the storagecapacitor may increase.

In order to decrease the parasitic capacitance, a thickness of the metalwirings (gate electrode, source electrode, and drain electrode) may beincreased to decrease the resistance thereof. However, referring to FIG.4B, when the thickness of the gate electrode 232 is increased, thethickness of the gate insulating layer 113 may be increased in order toprevent the short circuit due to the step height. The current drivingcapability of the third transistor 23 may decrease, increasing thecharging time of the storage capacitor, and making the driving of thelarge-sized and high-resolution display difficult.

With respect to a thin film transistor using the oxide active layer 234,the top-gate structure thin film transistor as in FIG. 4A may be used inorder to decrease the parasitic capacitance due to the above-describedoverlap. An oxide active layer may be used instead of the silicon activelayer 222 of FIG. 4A. The resistance of the doped regions L1 may bedecreased and the conductivity thereof may be increased by dopingremaining portions excluding the channel region L_(T) using the gateelectrode 224 as a mask. However, with respect to the transistor havingthe above structure, decreases in resistances of the source region L1and the drain region L2 by doping may not be facilitated different fromthe second transistor 22 having the silicon active layer 222, anddeviations in the characteristics of the thin film transistor may occuror the reliability thereof may be decreased when ion doping is performedto increase the conductivity.

The first transistor 21 according to the embodiment has characteristicsin which the parasitic capacitance may decrease, the on-state currentflowing in the thin film transistor may increase, and the off-stateleakage current may decrease in comparison to the second transistor 22and the third transistor 23 of the comparative examples.

FIG. 5 illustrates a cross-sectional view schematically illustrating theorganic light-emitting display apparatus 1 according to the embodiment.

The organic light-emitting display apparatus 1 of FIG. 5 may include afirst transistor region TRs, a second transistor region TRd, and a pixelregion PXL. The first transistor region TRs may include the firsttransistor 21 described in FIG. 3, and the second transistor region TRdmay include the second transistor 22 described in FIG. 4A. According toan embodiment, a switching transistor may be disposed in the firsttransistor region TRs and a driving transistor connected to a pixelelectrode 251 may be disposed in the second transistor region TRd.

A light-emitting device 25 may be disposed in the pixel region PXL, andthe light-emitting device 25 may include the pixel electrode 251, anintermediate layer 252, and a counter electrode 253.

The first transistor 21 is included in the first transistor region TRs.An off-state leakage current of the first transistor 21 may be lowerthan that of the second transistor 22. The first transistor 21 may beused as the switching transistor M1, in which the leakage currentsuppression characteristics are important, and the second transistor 22having high electron mobility may be used as the driving transistor M2,in which the effect of the leakage current is small. Also, with respectto the organic light-emitting display apparatus 1 having the structureas in FIG. 5, the leakage current of the first transistor 21 acting asthe switching transistor M1 may be prevented and simultaneously, theparasitic capacitance may not be generated, and the first transistor 21may be appropriate for driving the large-sized organic light-emittingdisplay apparatus 1.

Hereinafter, a method of manufacturing the organic light-emittingdisplay apparatus 1 according to an embodiment will be described withreference to FIGS. 6A through 6G.

FIG. 6A illustrates a cross-sectional view schematically illustrating afirst mask process for manufacturing the organic light-emitting displayapparatus 1 according to the present embodiment.

Referring to FIG. 6A, a buffer layer 111 may be formed on a substrate110 and a silicon semiconductor layer (not shown) may be formed on thebuffer layer 11. Then, a first silicon active layer 212 a and a secondsilicon active layer 212 b of a first transistor 21 and a silicon activelayer 222 of a second transistor 22 may be formed by patterning thesilicon semiconductor layer (not shown).

Although not illustrated in FIG. 6A, the silicon semiconductor layer(not shown) may be coated with a photoresist (not shown) and the siliconsemiconductor layer (not shown) may then be patterned byphotolithography using a first photomask (not shown) to form theabove-described first silicon active layer 212 a, second silicon activelayer 212 b, and silicon active layer 222. The first mask process byphotolithography may be performed through a series of processes, such asdeveloping, etching, and stripping or ashing, after the first photomask(not shown) is exposed with an exposure apparatus (not shown).

The silicon semiconductor layer (not shown) may be formed of amorphoussilicon or polysilicon. The polysilicon may be formed by crystallizationof the amorphous silicon. Various methods, such as rapid thermalannealing (RTA), solid phase crystallization (SPC), excimer laserannealing (ELA), metal induced crystallization (MIC), metal inducedlateral crystallization (MILC), and sequential lateral solidification(SLS), may be used as a crystallization method of the amorphous silicon.

FIG. 6B illustrates a cross-sectional view schematically illustrating asecond mask process for manufacturing the organic light-emitting displayapparatus 1 according to the present embodiment.

An oxide semiconductor layer (not shown) may be formed on the product ofthe first mask process of FIG. 6A, and an oxide active layer 212 c ofthe first transistor 21 may then be formed by patterning the oxidesemiconductor layer (not shown). The oxide active layer 212 c may bedisposed in a space between the first silicon active layer 212 a and thesecond silicon active layer 212 b, and as illustrated in FIG. 6B, theoxide active layer 212 c may be formed to partially overlap the firstsilicon active layer 212 a and the second silicon active layer 212 b.

The oxide active layer 212 c may include an oxide semiconductor. Forexample, the oxide semiconductor layer (not shown) may include an(In₂O₃)_(a)(Ga₂O₃)_(b)(ZnO)_(c) (G-I-Z-O) layer (where a, b, and c arereal numbers respectively satisfying conditions of a≥0, b≥0, and c≥0),and in addition, may include an oxide of a material selected from thegroup of Groups 12, 13, and 14 metallic elements, such as Zn, In, Ga,Sn, Cd, Ge, or Hf, and a combination thereof.

FIG. 6C illustrates a cross-sectional view schematically illustrating athird mask process for manufacturing the organic light-emitting displayapparatus 1 according to the present embodiment.

A gate insulating layer 113 may be formed on the product of the secondmask process of FIG. 6B, a first metal layer (not shown) is stacked onthe gate insulating layer 113, and the first metal layer (not shown) maythen be patterned. The first metal layer (not shown) may be formed as asingle layer or multilayers of one or more metals selected from thegroup of Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Ir, Cr, Li, Ca, Mo, Ti, W, andCu.

As a result of the patterning, a gate electrode 214 of the firsttransistor 21 and a gate electrode 224 of the second transistor 22 maybe formed on the gate insulating layer 113.

The resultant structure as described above is doped with ion impurities.N⁺ or P⁺ ions may be doped as ion impurities, and the first siliconactive layer 212 a, the second silicon active layer 212 b, and siliconactive layer 222 may be doped at a concentration of, e.g., about 1×10¹⁵atoms/cm³ or more.

The first silicon active layer 212 a, the second silicon active layer212 b, and silicon active layer 222 may be doped with ion impurities byusing the gate electrode 214 and the gate electrode 224 as self-alignedmasks, and electron mobilities of doping regions L1 may increase. In thefirst transistor 21 and the second transistor 22, remaining regionsexcluding the doping regions L1 may be channel regions L_(T).

FIG. 6D illustrates a cross-sectional view schematically illustrating afourth mask process for manufacturing the organic light-emitting displayapparatus 1 according to the present embodiment.

An interlayer insulating layer 115 may be formed on the product of thethird mask process of FIG. 6C, and the interlayer insulating layer 115may be patterned to form openings exposing the first silicon activelayer 212 a and the second silicon active layer 212 b.

FIG. 6E illustrates a cross-sectional view schematically illustrating aresult of a fifth mask process for manufacturing the organiclight-emitting display apparatus 1 according to the present embodiment.

Referring to FIG. 6E, a second metal layer (not shown) may be formed onthe product of the fourth mask process of FIG. 6D, and the second metallayer (not shown) may be patterned to simultaneously form a sourceelectrode 216 a and a drain electrode 216 b of the first transistor 21and a source electrode 226 a and a drain electrode 226 b of the secondtransistor 22.

The second metal layer (not shown) may be formed of two or more layersof different metals having different electron mobilities. For example,the second metal layer (not shown) may be formed of two or more layersof metals selected from the group of Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Ir,Cr, Li, Ca, Mo, Ti, W, Cu, and an alloy thereof.

FIG. 6F illustrates a cross-sectional view schematically illustrating aresult of a sixth mask process for manufacturing the organiclight-emitting display apparatus 1 according to the present embodiment.

Referring to FIG. 6F, a planarization layer 117 may be formed on theproduct of the fifth mask process of FIG. 6E, and the planarizationlayer 117 may be patterned to form a contact hole exposing the sourceelectrode 226 a or the drain electrode 226 b of the second transistor22.

The planarization layer 117 may be formed of an organic insulatinglayer. A general-purpose polymer (e.g., polymethyl methacrylate (PMMA)or polystyrene (PS)), a phenol group-containing polymer derivative, anacrylic polymer, an imide-based polymer, an arylether-based polymer, anamide-based polymer, a fluorinated polymer, a p-xylene-based polymer, avinylalcohol-based polymer, and a blend thereof may be used as theorganic insulating layer.

FIG. 6G illustrates a cross-sectional view schematically illustrating aresult of a seventh mask process for manufacturing the organiclight-emitting display apparatus 1 according to the present embodiment.

A third conductive layer (not shown) may be formed on the product of thesixth mask process of FIG. 6F, and the third conductive layer (notshown) may be patterned to form a pixel electrode 251 which is incontact with the source electrode 226 a or the drain electrode 226 b ofthe second transistor 22 through the contact hole formed in theplanarization layer 117.

The display apparatus may be a bottom-emission type display apparatus,and the third conductive layer (not shown) may be included as atransparent electrode The display apparatus may be a top-emission typedisplay apparatus, and the third conductive layer (not shown) may beincluded as a reflective electrode.

The display apparatus may be a bottom-emission type display apparatus,and the third conductive layer (not shown) may include at least one ormore selected from the group of indium tin oxide (ITO), indium zincoxide (IZO), zinc oxide (ZnO), indium oxide (In₂O₃), indium galliumoxide (IGO), and aluminum zinc oxide (AZO). Also, the pixel electrode251 may have a three-layer structure composed of transparent conductiveoxide layer/semi-transparent metal layer/transparent conductive oxidelayer.

The display apparatus may be a top-emission type display apparatus, anda reflective layer may be formed of Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Ir,Cr, Mg, or a combination thereof, and ITO, IZO, ZnO, In₂O₃, IGO, or AZOmay then be formed on the reflective layer.

FIG. 6H illustrates a cross-sectional view schematically illustrating aresult of an eighth mask process for manufacturing the organiclight-emitting display apparatus 1 according to the present embodiment.

A pixel-defining layer 118 may be formed on the product of the seventhmask process of FIG. 6G, and the eighth mask process for forming anopening exposing a top of the pixel electrode 251 may be performed.

The pixel-defining layer 118, for example, may be formed of an organicinsulating layer including a general-purpose polymer (e.g., PMMA or PS),a phenol group-containing polymer derivative, an acrylic polymer, animide-based polymer, an arylether-based polymer, an amide-based polymer,a fluorinated polymer, a p-xylene-based polymer, a vinylalcohol-basedpolymer, or a blend thereof.

As illustrated in FIG. 5, an intermediate layer 252 including an organicemission layer (not shown) may be formed on the product of the eighthmask process of FIG. 6H, and a counter electrode 253 may then be formed.

The intermediate layer 252 includes the organic emission layer thatemits, e.g., red, green, or blue light, and a low molecular weightorganic material or a polymer organic material may be used to form theorganic emission layer. The organic emission layer may be a lowmolecular weight organic layer formed of the low molecular weightorganic material, a hole transport layer (HTL) and a hole injectionlayer (HIL) may be disposed in a direction of the pixel electrode 251about the organic emission layer, and an electron transport layer (ETL)and an electron injection layer (EIL) may be stacked in a direction ofthe counter electrode 253. Various layers, in addition to the HIL, theHTL, the ETL, and the EIL, may be stacked and formed in variousimplementations.

In the above-described embodiment, described is an example in which aseparate organic emission layer may be formed for each pixel. Each pixelmay emit red, green, or blue light, and a pixel group that emits red,green, and blue light may constitute a single unit pixel. The organicemission layer may be formed on the entire pixel. For example, theplurality of organic emission layers that emit red, green, and bluelight may be vertically stacked or mixed to emit white light. A colorconversion layer for converting the emitted white light intopredetermined color or a color filter may be further included.

The counter electrode 253 opposite to the pixel electrode 251 isdisposed on the intermediate layer 252. The counter electrode 253 mayalso be formed of a transparent electrode or a reflective electrode. Atransparent electrode may be used as the counter electrode 253, thecounter electrode 253 may be formed in such a manner that a metal with alow work function, e.g., Li, Ca, LiF/Ca, LiF/Al, Al, Mg, or acombination thereof, may be deposited to face the organic emissionlayer, and an auxiliary electrode or a bus electrode line formed of atransparent conductive oxide, such as ITO, IZO, ZnO, or In₂O₃, may thenbe formed thereon. A reflective electrode may be used as the counterelectrode 253, and the counter electrode 253 may be formed by depositingLi, Ca, LiF/Ca, LiF/Al, Al, Mg, or a combination thereof on an entiresurface of a display portion. An organic material, such as a conductivepolymer, may be used as the pixel electrode 251 and the counterelectrode 253.

As described above, according to the one or more of the aboveembodiments, a thin film transistor array substrate, a displayapparatus, and a method of manufacturing the thin film transistor arraysubstrate may provide the following effects.

First, a parasitic capacitance of a thin film transistor may bedecreased.

Second, an off-state leakage current of a thin film transistor may bedecreased and an on-state current thereof may be increased.

Third, one or more embodiments provide a light-emitting displayapparatus that may have excellent device characteristics and displayquality.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of skill in the art as of thefiling of the present application, features, characteristics, and/orelements described in connection with a particular embodiment may beused singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwisespecifically indicated. Accordingly, it will be understood by those ofskill in the art that various changes in form and details may be madewithout departing from the spirit and scope of the present invention asset forth in the following claims.

What is claimed is:
 1. An organic light-emitting display apparatus,comprising: a substrate; a first transistor which includes a first gateelectrode, a first source electrode, a first drain electrode, and afirst active layer including an oxide active layer, the first gateelectrode being on the substrate with the oxide active layertherebetween; a second transistor which includes a second gateelectrode, a silicon active layer, a second source electrode, and asecond drain electrode including a same material and on a same layer asthe first source electrode and the first drain electrode, the secondgate electrode being on the substrate with the silicon active layertherebetween; and a light-emitting device including a pixel electrode,an intermediate layer, and a counter electrode, an intermediateinsulation layer covering the oxide active layer and the silicon activelayer, and on which the first source electrode, the first drainelectrode, the second source electrode, and the second drain electrodeare disposed, wherein the oxide active layer is operated as a channelregion in the first transistor, and the silicon active layer is operatedas a channel region in the second transistor.
 2. The organiclight-emitting display apparatus as claimed in claim 1, wherein theoxide active layer and the silicon active layer are on different layersfrom each other.
 3. The organic light-emitting display apparatus asclaimed in claim 1, wherein the first transistor is a switchingtransistor of the organic light-emitting display apparatus.
 4. Theorganic light-emitting display apparatus as claimed in claim 1, whereineach of the first source electrode and the first drain electrode doesnot overlap with the oxide active layer.
 5. The organic light-emittingdisplay apparatus as claimed in claim 1, wherein the silicon activelayer includes amorphous silicon or polysilicon.
 6. The organiclight-emitting display apparatus as claimed in claim 1, wherein theoxide active layer includes one or more of gallium indium zinc oxide(G-I-Z-O), an oxide of zinc (Zn), indium (In), gallium (Ga), tin (Sn),cadmium (Cd), germanium (Ge), or hafnium (Hf), and a combinationthereof.